Russell Libby, MD, founder and president of Virginia Pediatric Group, a primary care pediatric practice with three offices in northern Virginia, and president of the independent practice association HeathConnect IPA

Daniel J. Morelli, MD, primary care physician with UBMD Family Medicine (practice plan of the UB medical school) and interim chair, department of family medicine, University at Buffalo School of Medicine and Biomedical Sciences.

Peter T. Ostrow, MD, PhD, co-director, Research Center for Stroke and Heart Disease and associate professor of pathology and neurology, University at Buffalo

Horvitz: "The Annals of Internal Medicine published a study that brings it out of the Stone Age to finally give some credence to lower carbohydrate diets. For those who feel it is quack science, I suggest you read the abundant research that is out there if you just open your eyes, ears, and mind."

Morelli: "It's promising to know that when you offer a patient a diet low in carbohydrates, you don't see adverse lipid results."

Frost: "This study offers additional information on how to address the obesity epidemic in this country and its negative health consequences. There is more and more research in this area, which will help us give our patients appropriate and effective guidance."

Libby: "One of the most difficult things to do is motivate your obese patients to lose weight, for any reason. It is not that the desire is not there, it is more that the individual effort requires the commitment and perseverance few can muster. The fact that the best outcome was 11.5 lbs after 1 year is testament to that. The long-term outlook for those people is not rosy and is still likely to become hypertensive, and develop type 2 diabetes."

Ostrow: "According to the report, people on the low-fat diet lost an average of approximately 4 lbs during the study, while those on the low-carb diet lost almost 12 pounds. That's an advantage of 7.7 pounds for the low-carb diet. But is it really?"

Carb Confounders and Confusion

Morelli: "This study has a small, select population, with about 75 participants in the experimental group. The study provided extensive dietary education and counseling, something most insurers do not support."

Gnanadesikan: "It stimulates some thought, to be sure, but I don't think it is sufficient to conclude that low-carb is right for everyone. The lack of sufficient self-reporting data points is a major limitation that makes the data less than completely clear."

Katz: "If this had been a study of low-fat versus low-carb diets, it would have been silly and archaic. The wholesale cutting of these macronutrient classes without regard for the foods involved is discredited nonsense. Cutting 'carbs' would mean cutting vegetables and fruits; cutting 'fat' would mean cutting nuts, seeds, and avocado. These are not sensible practices."

Weatherly: "This study watched low-risk people (160 of them) for 1 year to find a difference in 'clinical' cardiovascular disease endpoints. Hmm. Smells of surrogate markers and lipid theory in too short of a time span to be clinically relevant."

Katz: "And, in fact, this was not a study of low-carb versus low-fat diets. The study compared a low-carb diet with a minimally fat-reduced diet. Participants randomized to the low-carb group were asked to cut their carbohydrate intake by about 75% from baseline; those in the so-called low-fat group, a paltry 5% from their baseline.

"The much more restrictive low-carb diet wound up being considerably lower in calories throughout the study -- and for that reason participants in that group lost more weight. All of the participants were obese at baseline and had impaired cardiac risk measures because of obesity -- so those who lost more weight had more improvement in cardiac risk for that reason."

Ostrow: "Let's look at the calories, which were claimed to be about the same for the two groups: Those on a low-fat diet reportedly consumed an average of 1,527 calories per day, while those on a low-carbohydrate diet took in an average of 1,448 calories. That's 79 calories a day less, which doesn't seem like much, but if you do that every day over a year it becomes a total of almost 29,000 calories. If we use the standard that 3,500 calories equals 1 pound, the people on the low-carb diet would have an additional weight loss greater than 8 lbs. That means the additional weight loss could be accounted for entirely by caloric intake, without regard for fat or carbohydrates."

Katz: "Also, the low-carb diet was low in fiber; that is to be expected. But the so-called low-fat diet was exactly as low in fiber, at about 16 grams per day -- indicating that this was neither a low-fat diet, nor even a diet comprised of wholesome plant foods. Essentially, this diet compared a more restrictive, lower calorie, reduced carbohydrate diet -- with a diet that was, apparently, not very good and not much changed from baseline."

In Practice

Morelli: "I anticipate that most physicians will want to see outcomes in populations which mimic their practice profiles, e.g., patients with chronic illness such as diabetes. I tell patients who need to lose weight to start by monitoring caloric intake with a diet diary and evaluating exercise routines."

Horvitz: "I have been an advocate of lower-carb diets for over a decade, not because I read a book about it, but because it works extremely well in my practice, especially in the metabolically challenged."

Libby: "I do believe the carbohydrate part of a diet is the hardest to control because of the gratification and short satiety we get from those foods. It doesn't, however, make eating fat a good alternative. The ideal diet would decrease both food groups and, regardless of contradictory assertions, be enhanced by a good exercise routine."

Gnanadesikan: "It's an important responsibility of doctors to function as data interpreters for our patients, who read the headlines but may not fully understand the ramifications of the 'fine print.' Reading this study is just such a case. 'Weight, in and of itself, is just a number.' This is a phrase I've uttered dozens of times to patients. Is it an important number? Yes. But it's not a be-all or end-all, and people reading studies need to understand that."

Weatherly: "If a patient would rather do low-fat diet for ASCVD risk reduction, is this enough to have me tell him, 'The evidence is clear! It must be low-carb'? No. Don't put out their fire, light them up! The 'new diet' doesn't translate into lifestyle changes too often to worry about which diet they want."

Frost: "I discuss different diets with my patients to find the diet that works best for them given their lifestyle and preferences, with a focus on healthy eating and increased physical activity."

Weatherly: "I am guessing that the old 'exercise for 30 min a day and get to/maintain a good body fat/weight/BMI' is noninferior in clinically relevant measures at 10 years."

Katz: "By implying that this study revealed anything meaningful about low-carb versus low-fat diets, a whole lot of harm has been done by the paper and the associated media coverage. This study simply did not show what the headlines claim."

Friday Feedback is a feature that presents a sampling of opinions solicited by MedPage Today in response to a healthcare issue, clinical controversy, or new finding reported that week. We always welcome new, thoughtful voices. If you'd like to participate in a Friday Feedback, or suggest a topic, drop us a line or two.

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